1. Field of the Invention
This invention is in the field of visual field screening.
2. Background Information
On a world-wide basis, glaucoma is one of the leading causes of blindness. Unlike cataract blindness, which is correctable with modem surgical techniques, blindness from glaucoma is permanent. The target organ of glaucoma is the optic nerve, which transmits signals of light from the retina to the brain. No known method is available for repairing, or transplanting, an injured optic nerve. Millions upon millions of patients throughout the world have glaucoma and are completely unaware of this. The particularly sad aspect of glaucoma blindness is that it is generally preventable with proper diagnosis and treatment.
A major diagnostic problem is that, in many areas of the world, medical resources are scarce to the point of being virtually nonexistent. Therefore, many diseases which are readily treatable, sadly, go about their devastating business completely unchecked. Glaucoma, which causes absolute, total blindness when untreated, is no exception.
A second major diagnostic problem is that visual loss from glaucoma is, almost without exception, painless. The patient is unaware of the ravages of glaucoma until it is too late. With the use of an instrument called a "tonometer" to measure the intraocular pressure, the diagnosis can be made whenever the pressure within the eye is significantly elevated. However, tonometry is not available in many parts of the world; and many patients have the "low-tension" form of glaucoma in which the intraocular pressure is completely normal. Therefore, reliance upon tonometry, in areas of the world where this is available, frequently leads to a blatantly false sense of security. The patient is told that glaucoma is not present, when, in reality, the disease is insidiously attacking the patient's optic nerve, causing irreversible neurological damage to the visual system.
Because of the limitations associated with tonometry, most eye physicians attest that visual field testing is mandatory for glaucoma diagnosis and treatment. In fact, visual field testing is currently considered to be the gold standard for measuring the function of the optic nerve and the presence, or absence, of glaucoma. Visual field testing is generally an expensive proposition, however, with significant fees being charged for each test. Often, there is a physician or optometric examination charge in addition to the fee for the visual field test itself. Another major hurdle is that the patient must make an appointment for an eye examination, which is sometimes difficult. Additionally, since glaucoma is generally painless and totally devoid of symptoms until late stages of the disease, for the vast majority of people, no concrete motivation is present to seek professional help when nothing hurts. The upshot of this is that the diagnosis of glaucoma is all too frequently never made until it is too late.
Furthermore, in countries which are economically disadvantaged, visual field testing machines are prohibitively expensive.